Dyes Adsorbed at Ag‐Colloids: Substitution of Fluorescence by Similarly Efficient Surface Fluorescence and Surface Raman Scattering

With the addition of Ag‐sol to extremely diluted rhodamine 6G solutions (ca. 10−10 M/l) the prevalent fluorescence can be replaced by surface fluorescence and surface enhanced resonance Raman scattering (SERRS) of similar intensity, however only in presence of coadsorbed anions such as chloride. For strong bands the Raman cross sections are as high as 10−19 cm2 sr−1 molecule−1. Referred to the extinction of the sol which is much larger than that of the dye solution, the mean quantum yield for the surface Raman scattering is estimated to 0.0004. In addition, SERRS consisting of a set of fundamental vibrations, overtones and combination modes and a broad continuum shows throughout the spectral range a significant, but identical polarisation (I(sp): I(ss) = 0.55), whereas the solution as well as surface fluorescence is completely depolarised.